#include <cstdio>

int main( )
{
    int n, total;
    while ( scanf("%d", &n) != EOF )
    {
        total = 0;
        while ( n >= 0 )
        {
            total = total + n / 2 + 1;
            n -= 3;
        }
        printf("%d\n", total);
    }
    return 0;
}
